Aircraft propulsion system



June 7, 1966 H. c. HIGGINS 3,254,725

AIRCRAFT PROPULS ION SYSTEM Original Filed July 17, 1963 2 Sheets-Sheet1 FIG. I I2 .0

FIGZ

INVENTOR. HARRY C. HIGGINS June 7, 1966 H. c. HIGGINS AIRCRAFTPROPULSION SYSTEM 2 Sheets-Sheet 2 Original Filed July 1'7, 1963INVENTOR HARRY C. HIGGINS United States Patent 3,254,725 AIRCRAFTPROPULSION SYSTEM Harry C. Higgins, Wichita, KHERS., assignor to TheBoeing Company, Wichita, Kane, a corporation of Delaware Originalapplication July 17, 1963, Ser. No. 295,722, now Patent No. 3,185,408,dated May 25, 1965. Divided and this application Aug. 10, 1964, Ser. No.393,468

6 Claims. (Cl. 170-16027) This is a division of U.S. application SerialNo. 295,722, filed July 17, 1963, now Patent No. 3,185,408, for AircraftPropulsion System.

This invention relates to aircraft propulsion systems for providing anairplane with the capability of hovering, loitering, short take off andlanding, and/or vertical take off and landing.

One of the objects of this invention is the provision of a novelaircraft propulsion system for providing an airplane with a capabilityof hovering, loitering, short take off and landing, and/ or verticaltake off and landing.

Another object of this invention is the provision of a novel propulsionsystem, as set forth in the preceding object, having a simple,lightweight, and economically manufactured and installed retractablerotor adapted to be driven by a conventional aircraft engine.

Another object of this invention is the provision of an aircraftpropulsion system having a rotor that can be controllably tilted so asto provide vertical and/or thrust components, the blades of the rotorbeing automatically retracted or folded when the drag forces on therotor exceeds the thrust on the rotor.

Yet another object of this invention is the provision of a novelaircraft propulsion system adapted to be installed on an airplane so asto provide the airplane with a shorter take off and landing capabilityand/ or vertical take off and landing capability, the propulsion systemhaving a rotor adapted to be driven by the conventional propulsionsystem of the airplane and being tiltable to any desired position forobtaining horizontal and/ or vertical thrust components.

Another object of this invention is the provision of simple, reliableand inexpensive means for controlling the rotor of the novel propulsionsystem set forth in the preceding object.

The invention further resides in certain novel features ofconstructions, combinations, and arrangements of parts and furtherobjects and advantages of the invention will be apparent to thoseskilled in the art to which it pertains from the following descriptionof the present preferred embodiment thereof described with reference tothe accompanying drawings, which form a part of this specification,wherein the same reference numerals indicate corresponding partsthroughout the several views, and in which:

FIG. 1 is a side elevational view of a conventional airplane embodyingthe invention, the airplane being shown in a vertical or hovering flightmode;

FIG. 2 is a view similar to FIG. 1 but showing the airplane in a normalforward flight mode with the novel propulsion system providing forwardthrust, the novel propulsion system having rotors adapted to be foldedor retracted as is shown in hidden outline when aerodynamic drag thereonexceeds forward thrust;

FIG. 3 is an enlarged fragmentary view of a portion of the novelpropulsion system in FIG. 2, but with parts broken away and in sectionto show certain additional details thereof; and

FIG. 4 is an enlarged bottom view of a rotor portion of the propulsionsystem as viewed along line 44 in FIG. 3.

Patented June 7, 1966 It is to be understood that the invention is notlimited to the details of construction and the arrangements of partsshown in the drawings and hereafter described in details, but is capableof being otherwise embodied and of being practiced and carried out invarious ways. It 1s to be further understood that the terminologyemployed herein is for-the purpose of description and there is nointention to herein limit the invention beyond the requirements of theprior art.

Referring to FIG. 1, reference numeral 10 indicates generally anairplane having a fuselage 11, a fixed wing 12, and an empennagecomprising a vertical stabilizer and a control surface 13 and horizontalstabilizers and control surfaces 14. The wing 12 is connected to thefuselage 11 near the top side thereof for providing adequate groundclearance for the operation of a novel propulsion system embodying theinvention. A pair of conventional airplane engines 15 are slung belowthe wing 12 on either side of the fuselage 11 and drive conventionalpropellers 16. A large rotor means indicated generally by referencenumeral 20 is pivotally connected to a horizontal journal shaft 21 atthe aft end of the conventional engine 15. The large rotor means 20 maybe referred to as an auxiliary propulsion system and the aircraft engine15 may be referred to as a primary or conventional propulsion system.The auxiliary aircraft propulsion system 20 comprises large fold-able orretractable rotors 22, 23 driven by a drive shaft 24 pivotally connectedat 21 to the port engine 15. A faired frustoconical support member 25encloses the drive shaft 24 and provides a streamlined housing forreducing aerodynamic drag minimizing aerodynamic turbulence. The member25 has a pair of arms pivotally connected to the shaft 21.

As seen in FIG. 1 the airplane 10 is in a vertical or hovering mode forvertical take off or landing. The auxiliary propulsion system 26therefore has its drive shaft 24 vertically aligned and extendingthrough or near the center of pressure of the wings 12 so as to minimizeany upset in the flight stability of the aircraft due to shiftingcenters of pressure and/or centers of weight.

FIG. 2 shows the auxiliary propulsion system 20 with its drive shaft 24horizontal aligned with and coincidental with the direction of flight ofthe aircraft 10. In this particular horizontal flight mode the largerotors 22, 23 are fully extended for augmenting the forward thrust ofthe propellers 16 of the conventional propulsion system 15. When theaerodynamic drag on the rotors 22, 23 exceeds the thrust providedthereby the rotors 22, 23 are forced into a retracted or folded positionas shown in hidden outline in FIG. 2. There is nothing to hold therotors 22, 23 in a retracted position other than aerodynamic drag.However, there are state of the art devices available for locking therotor blades 22, 23 in retracted posi tion. The rotor blades 22, 23 maybe quickly retracted in flight by disengaging the auxiliary propulsionsystem 20 from the drive of the conventional propulsion system 15preferably by means of .an electromagnetic clutch 26, FIG. 3.

As seen in FIG. 3 the clutch 26 has a driving element 26a carried by adrive shaft 27 of the conventional propulsion system 15 adapted todrivingly engage the element 26b fixed to a driven shaft 28. The drivenshaft 28 drives the drive shaft 24 of the auxiliary propulsion system 20through a differential mechanism comprising a beveled ring gear 30 andbeveled driven pinion gears 31 and 32. The pinion gear 31 is fixed tothe driven shaft 28,. The driven shaft 28 is journaled in journalbearing assembly 33 carried by a supporting member 34 within the housingof the primary propulsion system 15. The driven or output pinion 32 isfixed to and drives the v drive shaft 24. The ring gear 30 is journaledon the 3 journal shaft 21. The shaft 21 is carried by a supportingmember within the housing of the conventional propulsion system 15.

As pointed out hereinabove, the auxiliary propulsion system 20 can beswung from the forward flight mode as shown in FIG. 3 downward to avertical position for vertical flight mode as shown in hidden outline inFIG. 3. The drive shaft 24 can be tiltably adjusted -to any positionbetween the horizontal and vertical flight mode by means of a push-pullpiston rod 35 that can be extended or retracted by means of a doubleacting hydraulic motor 36. The inner end of the push-pull rod 35 isfixed'to a piston, not shown, slidably disposed in the cylindricalhousing of a motor 36. The outer end of the rod 35 is pivotallyconnected to a collar 37 carried by the drive shaft 24 by means of apivot pin 38. The drive shaft 24 is journaled in the collar 37 by meansof antifriction bearing 39. The collar 37 is fixed against movementaxailly of the drive shaft 24. The housing of the motor 36 has anaxially extending flange 40 pivotally connected by a pin 41 to a supportbracket 42. The bracket 42 is fixed in a cnventional manner to a supportplate 43 carried within the housing of the conventional propulsionsystem 15.

As can be seen in FIG. 3, when the motor 36 retracts the push-pull rod35 the driven pinion 32 carried by the shaft 24 is caused to walk in aclockwise direction around the ring gear 30 to a vertical position asshown by hidden outline. When the auxiliary propulsion system 20 isproviding vertical and/ or horizontal thrust components additionalstructure may be needed or desired to transmit the thrust to theairplane via the wings 12. This additional structure does not form apart of this invention and can be provided in a manner well-known in theart.

The pitch of the rotor blades 22 and 23 can be uniformly andsimultaneously adjusted by operating a coaxial control cable 44. Both ofthe rotor blades 22 and 23 are identically operated. The cable 44 hasits outer end fixed to a plate 45 journaled on antifriction bearings 46carried by an outer end of an axially slidable non-rotatable rotor pitchadjusting tube 47. A forward end of the tube 47 bears against an helicalspring 48. The spring 48 is buttressed against a shoulder of a rotor hub50 fixed to and driven by the rotor shaft 24.

As can be seen in FIG. 3 the rotor shaft 24 is hollow or tubular forproviding for the passage of the control cable 44 therethrough. Theopposite end of'the control cable 44 extends between two idler guidepulleys connected to the shaft 21 and is adapted to be controlled by thepilot of the aircraft or alternatively may be controlled automaticallyby conventional means that do not form a part of this invention. Forexample, the cable 44 may be wound on a reel, not shown, that is drivenand controlled by a synchronous motor in a known manner.

The helical spring 48 constantly urges the propeller pitch tube 47axially outwardly or rearwardly whereby the rotors 22, 23 are urged to afully feathered position. A rotor pitch control arm 51 has one endpivotally connected at 52 to a laterally and diametrically extending arm47a of the forward end of the tube 47, FIG. 4, and the other endpivotally connected at 53 to pitch control lever 54. The lever 54 isfixed to a rotor blade root shaft 55 of the rotor blade 22. The rootshaft 55 extends completely through the rotor hub 50 and is pivotallyconnected by a pin 56 to an inner shank end 22a of the rotor blade 22.The pin 56 permits the rotor blade 22, when fully feathered, to befolded in an aft direction axially along the drive shaft 24. The rootshaft 55 is pivotally mounted or journaled in the hub 50 by means of asingle row of antifriction assemblies 57 and 58 in the opposite endsthereof.

The rotor shaft 24 is journaled by two double row antifriction bearingassemblies 60 in an aft end of the faired support member 25.

The pitch control tube 47 is slidably disposed upon an aft extendingtubular segment 61 forming an extension of the drive shaft 24. Thesegment 61 is fixed to the hub 50 and the shaft 24. The tube 47 isnon-rotatable in the sense that it does not rotate or turn relative tothe tube segment 61 but does rotate with the drive shaft 24, rotor hub50, and the tube segment 61. Pivotally mounted on the inner end of therotor 22 is a collar 62 having a flange fixed thereto for pivotallysupporting a guide link 63 by means of a pivot pin 64. The other end ofthe guide link 63 is pivotally connected to a flange of a collar 65 bymeans of a pivot pin 66. The collar 65 is slidably disposed over thepitch control collar 47. A coil spring 67, disposed about and encirclingthe tube 47, is buttressed by a flange 47o at the outer end of the tube47. The spring 67 resiliently urges the collar 65 axially towards therotor hub and acts to resist the retracting or folding of the rotorblades 22, 23. The tension of the spring 67 is adjusted so as to preventthe folding of the blades 22, 23 while the aircraft is parked. Theadvantage of this feature is that when the rotor shaft is in thevertical mode and the aircraft is parked the spring 67 will prevent theblades 22 and 23 from dropping down and touching the ground. However,when aerodynamic drag forces exceed the thrust forces of the rotorblades 22, 23 the blades will be urged rearwardly int-o a retractedposition as hereinabove described.

As seen in FIG. 4, the rotor blade root shaft is disposed parallel toand coplanar with a rotor blade root shaft 7 t} of the rotor blade 23'.However, both the rotor blade root shafts 55 and 7 0 are disposedlaterally on either side of the longitudinal axis of the drive shaft 24.The pitch of the rotor blade 23 is controlled by a pitch control arm 71having one end pivotally connected at 72 to a laterally anddiametrically extending arm 47b opposite to the arm 47a. The other'endof the pitch control arm 71 is pivotally connected at 73 to a pitchcontrol lever 74, FIG. 4. A collar 75 is pivotally mounted on the rotor23. The collar 75 has a flange fixed thereto for pivotally sup-porting aguide link 76 by means of a pivot pin 77. The other end of the guidelink 76- is pivotally connected to a flange of the collar 65 by means ofa pivot pin 78.

It will be understood that this invention can be modified to adapt it tovarious circumstances and conditions, and it is accordingly desired tocomprehend within the purview of this invention such modifications asmay be considered to fall within the scope of the appended claims.

What is claimed is:

1. In an aircraft propulsion system, rotor blade means, root shaft meanspivotally connected about a transverse axis thereof to said rotor meansin such a manner as to permit said rotor means to be folded, drive shaftmeans adapted to be drivingly connected to prime mover means, hub meansconnected to said drive shaft means and pivotally supporting said rootshaft means therein for permitting the pitch adjustment of said rotormeans, means forming rotor pitch adjusting tube means slidably disposedabout said drive shaft means, linkage means connecting said root shaftmeans to said rotor pitch adjusting tube means for causing change ofrotor pitch with the axial movement of said rotor pitch adjusting tubemeans, first spring means disposed about said drive shaft means andbearing against said hub means and urging said rotor pitch adjustingtube means away from said hub means and causing said root shaft meansand said rotor means to be turned to a fully feathered position, meansfor adjusting the axial position of said rotor pitch adjusting tubemeans including adjustable cable means connected thereto and extendingaxially of said drive shaft means for being operated from a remoteposition, first collar means slidably disposed about said rotor pitchadjusting tube means, second collar means journaled about said rotormeans adjacent said root shaft means, guide link means pivotallyconnected to said first collar means and to said second collar means,second spring means disposed about and bearing against said rotor pitchadjusting tube means and urging said first collar means toward saidrotor means for urging said rotor means to an erect operable position,said second spring means being strong enough to prevent the retractionof said rotor means until drag forces on said rotor means exceed anythrust generated by said rot-or means by an amount suflicient tocompress said second spring means, horizontal shaft means adapted to becarried by the aircraft, faired support means pivotally connected tosaid horizontal shaft means and journaling said drive shaft meanstherein,'differential gear means interposed in said drive shaft meansand having a beveled ring gear journaled on said horizontal shaft meansand a first pinion gear drivingly connected to a driven portion of saiddrive shaft means and a second pinion gear connected to a drivingportion of said drive shaft means, double acting fluid motor meanshaving a cylinder adapted to be pivotally connected to the airplane anda push-pull rod pivotally connected to and journaled on said drivenportion of said drive shaft means for pivotally moving said drivenportion of said drive shaft means from a horizontal position coaxialwith said driving portion of said drive shaft means downwardly to avertical position by retracting said fluid motor means in a verticalplane defined by said drive shaft means, and disengageable clutch meansin said driving portion of said drive shaft means.

2. In an aircraft propulsion system, rotor blade means, root shaft meanspivotally connected about a transverse axis thereof to said rotor meansin such a manner as to permit said rotor means to be folded, drive shaftmeans adapted to be drivingly connected to prime mover means, hub meansconnected to said drive shaft means and pivotally supporting said rootshaft means therein for permitting the pitch adjustment of said rotormeans, means forming rotor pitch adjusting tube means slidably disposedabout said drive shaft means, linkage means connecting said root shaftmeans to said rotor pitch adjusting tube means for causing change ofrotor pitch with the axial movement of said rotor pitch adjusting tubemeans, first spring means disposed about said drive shaft means andbearing against said hub means and urging said rotor pitch adjustingtube means away from said hub and causing said root shaft means and saidrotor means to be turned to a fully feathered position, means foradjusting the axial position of said rotor pitch adjusting tube meansincluding adjustable cable means connected thereto and extending axiallyof said drive shaft means for being operated from a remote position,first collar means slidably disposed about said rotor pitch adjustingtube means, second collar means journaled about said rotor meansadjacent said root shaft means, guide link means pivotally connected tosaid first collar means and to said second collar means, second springmeans disposed about and bearing against said rotor pitch adjusting tubemeans and urging said first collar means toward said rotor means forurging said rotor means to an erect operable position, said secondspring means being strong enough to prevent the retraction of said rotormeans until' drag forces on saidrotor means exceed any thrust generatedby said rotor means by an amount sufficient to compress said secondspring means, horizontal shaft means adapted to be carried by theaircraft, faired support means pivotally connected to said horizontalshaft means and journaling said drive shaft means therein, differentialgear means interposed in said drive shaft means and having a beveledring gear journaled on said horizontal shaft means and a first piniongear drivingly connected to a driven portion of said drive shaft meansand a second pinion gear connected to a driving portion of said driveshaft means, and means pivotally moving said driven portion of saiddrive shaft means from a horizontal position downwardly to a verticalposition in a vertical plane defined by said drive shaft means.

3. In an aircraft propulsion system, rotor blade means,

root shaft means pivotally connected about a transverse rotor pitchadjusting tube means away from said hub means and causing said rootshaft means and said rotor means to be turned to a fully featheredposition, means for adjusting the axial position of said rotor pitchadjusting tube means including adjustable cable means connected theretoand extending axially of said drive shaft means for being operated froma remote position, first collar means slidably disposed about said rotorpitch adjusting tube means, second collar means journaled about saidrotor means adjacent said root shaft means, guide link means pivotallyconnected to said first collar means and to said second collar means,second spring means disposed about and bearing against said rotor pitchadjusting tube means and urging said first collar means toward saidrotor means for urging said rotor means to an erect operable position,said second spring means being strong enough to prevent the retractionof said rotor means until drag forces on said rotor means exceed anythrust generated by said rotor means by an amount suificient to compresssaid second spring means, horizontal shaft means adapted to be carriedby the aircraft, f-aired support means pivotally connected to saidhorizontal shaft means and journaling said drive shaft means therein,and means for pivotally moving said rotor means from a horizontalposition downwardly to a vertical position and back to a horizontalposition.

4. In an aircraft propulsion system, rotor blade means, root shaft meanspivotally connected about a transverse axis thereof to said rotor blademeans in such a manner as to permit said rotor blade means to be folded,drive shaft means adapted to be drivingly connected to prime movermeans, hub means connected to said drive shaft means and pivotallysupporting said root shaft means therein for permitting the pitchadjustment of said rotor blade means, means forming rotor pitchadjusting tube means slidably disposed about said drive shaft means,link-age means connecting said root shaft means to said rotor pitchadjusting tube means for causing change of rotor pitch with the axialmovement of said rotor pitch adjusting tube means, first spring meansdisposed about said drive shaft means and bearing against said hub meansand urging said rotor pitch adjusting tube means away from said hubmeans and causing said root shaft means and said rotor blade means to beturned to a fully feathered position, means for adjusting the axialposition of said rotor pitch adjusting tube means including adjustablecable means connected thereto and extending axially of said drive shaftmeans for being operated from a remote position, first collar meansslidably disposed about said rotor pitch adjusting tube means, secondcollar means journaled about said rotor blade means adjacent said rootshaft means, guide link means pivotally connected to said first collarmeans and to said second collar means, second spring means disposedabout and bearing against said rotor pitch adjusting tube means andurging said first collar means toward said rotor blade means for urgingsaid rotor blade means to an erect position, and said secondspring meansbeing strong enough to prevent the folding of said rotor blade meansuntil drag forces on said rotor blade means exceed any thrust generatedby said rotor means by an amount sufficient to compress said secondspring means.

5. In an aircraft propulsion system, rotor blade means, root shaft meansconnected to said rotor means, drive shaft means adapted to be drivinglyconnected to prime mover means, hub means connected to said drive shaftmeans and pivotally supporting said root shaft means therein forpermitting the pitch adjustment of said rotor means, means forming rotorpitch adjusting tube means encircling and slidably disposed about saiddrive shaft means, linkage means connecting said root shaft means tosaid rotor pitch adjusting tube means for causing change of rotor pitchwith the axial movement of said rotor pitch adjusting tube means, springmeans disposed about said drive shaft means and bearing against said hubmeans and urging said rotor pitch adjusting tube means away from saidhub means and causing said root shaft means and said rotor means to beturned to a fully feathered position, means for adjusting the axialposition of said rotor pitch adjusting tube means, collar means slidablydisposed about said rotor pitch adjusting tube means, means pivotallymoving said drive shaft means from a horizontal position downwardly to avertical position and back to a horizontal position in a vertical planedefined by said drive shaft means, and disengageable clutch means insaid drive shaft means.

6. In an aircraft propulsion system, rotor blade means, root shaft meanspivotally connected about a transverse axis thereof to said rotor meansin such a manner as to permit said rotor means to be folded, drive shaftmeans adapted to be drivingly connected to prime mover means, hub meansconnected to said drive shaft means and pivotally supporting said rootshaft means therein, first collar means encircling and slidably disposedabout said drive shaft means, second collar means journaled about saidrotor means adjacent said root shaft means, guide link means pivotallyconnected to said first collar means and to said second collar means,and spring means disposed about and carried by said drive shaft meansand urging said first collar means toward saidrotor means for urgingsaid rotor means to an erect operable position, and said spring meansbeing strong enough to prevent the retraction of said rotor means untildrag forces on said rotor means exceed any thrust generated by saidrotor means by an amount sufiicient to compress said spring means.

FOREIGN PATENTS 1/1909 France. 11/1945 Great Britain.

25 MARK NEWMAN, Primary Examiner.

JULIUS E. WEST, SAMUEL LEVINE, Examiners.

W. E. BURNS, Assistant Examiner.

6. IN AN AIRCRAFT PROPULSION SYSTEM, ROTOR BLADE MEANS, ROOT SHAFT MEANSPIVOTALLY CONNECTED ABOUT A TRANSVERSE AXIS THEREOF TO SAID ROTOR MEANSIN SUCH A MANNER AS TO PERMIT SAID ROTOR MEANS TO BE FOLDED, DRIVE SHAFTMEANS ADAPTED TO BE DRIVINGLY CONNECTED TO PRIME MOVER MEANS, HUB MEANSCONNECTED TO SAID DRIVE SHAFT MEANS AND PIVOTALLY SUPPORTING SAID ROOTSHAFT MEANS THEREIN, FIRST COLLAR MEANS ENCIRCLING AND SLIDABLY DISPOSEDABOUT SAID DRIVE SHAFT MEANS, SECOND COLLAR MEANS JOURNALED ABOUT SAIDROTOR MEANS ADJACENT SAID ROOT SHAT MEANS, GUIDE LINK MEANS PIVOTALLYCONNECTED TO SAID FIRST COLLAR MEANS AND TO SAID SECOND COLLAR MEANS,AND SPRING MEANS DISPOSED ABOUT AND CARRIED BY SAID DRIVE SHAFT MEANSAND URGING SAID FIRST COLLAR MEANS TOWARD SAID ROTOR MEANS FOR URGINGSAID ROTOR MEANS TO AN ERECT OPERABLE POSITION, AND SAID SPRING MEANSBEING STRONG ENOUGH TO PREVENT THE RETRACTION OF SAID ROTOR MEANS UNTILDRAG FORCES ON SAID ROTOR MEANS EXCEED ANY THRUST GENERATED BY SAIDROTOR MEANS BY AN AMOUNT SUFFICIENT TO COMPRESS SAID SPRING MEANS.